Patients with acute myeloid leukemia (AML), aggressive blood cancer, often are treated by stem cell transplantation in which donor hematopoietic cells transplanted to a patient. Then the donor immune cells attack and kill leukemia cells. But even with the success of the treatment in many patients subsequently relapse.

A study conducted by the School of Medicine at Washington University, explains why many patients with AML experience relapse after stem cell transplantation, and offers a new therapeutic approach that could restore patients relapsing back into remission. The study was published Oct. 31 in the «New England Medicine.» Magazine.

Scientists have carried out DNA sequencing of AML cells obtained from 15 patients whose disease has returned after a stem cell transplant, and 20 patients who had relapsed after chemotherapy. They found that mutations that were present in recurrent AML cells after transplantation were similar to the mutations in the cells after chemotherapy.

The researchers also found a significant difference in the patterns of gene expression cells. Cells patients relapsing after transplantation, often resulted in a significant decrease of gene expression associated with recognition of cancer cells by the immune system. in other words, when the cancer recurred, he recurred in "stealth mode". These hidden leukemia cells were deprived of proteins that donor T cells used to identify risk. When the donor immune cells may not detect the cell leukemia, T-cells can not destroy them.

The researchers also identified a natural signaling molecule - interferon gamma - which forced the hidden leukemia cells to manifest itself again. This provided a new therapeutic option for patients with AML who relapse occurred.

"When we treated AML cells obtained from patients with relapse after transplantation, interferon gamma, we could make visible the" invisible "immune markers. This suggests that the process is reversible, "- the researchers noted.

Interferon gamma is FDA approved for the treatment of a rare condition, chronic granulomatous disease - a hereditary immune disorder, which leads to frequent and life-threatening bacterial or fungal infections.